It is possible to increase the network capacity of a basic service set (BSS) using Uplink (UL) Multi-user Multiple Input, Multiple Output (MU MIMO). With UL MU MIMO, multiple STAs are permitted to simultaneously (in time and frequency) transmit to a multiple-antenna access point (AP) and the resulting signals are separated by the AP's MIMO equalizer. FIG. 1, shown generally as 100, shows an UL MU MIO procedure when explicit ack is utilized. If implicit ack is used, the STAs do not need to send the BAR frames. Upon receiving the data frames from the STAs, the AP sends back block acks (BAs) sequentially. BAs are separated by Reduced Inter Frame Space (RIFS).
Current wireless networks which operate in compliance with the existing Institute for Electronic and Electrical Engineers (802.11) standard do not support the use of UL MU MIMO and thus improvements are needed in UL MU MIMO techniques.
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